Oscillation generator



Fb. 1, 1949. HUGE I OSCIILLATION GENERATOR Filed July 17, 1944 INVENTOR. ,HE/WP). M. HUGE BY AT RN Y5.

Patented Feb. 1, 1949 UNITED STATES PATENT OFFICE anodes? i OSCILLATION GENERATOR Henry M. Huge, Lorain, Ohio, assignon'by mesne assignments, to Lorain Products Corporation, Lorain, Ohio, a corporation of Ohio Application July 17, 1944,. S eria'l No. 545,278

This invention relates to vacuum tube oscillators and more particularly to oscillators capable of generating oscillations which periodically vary in amplitude or frequency or both.

One of the objects of this invention is to produce a signaling tone initially having a very small amplitude which gradually increases to a large amplitude.

It is a further object of my invention to generate an oscillation which simultaneously changes in amplitude and frequency over a given time interval.

Another object of my invention is to construct an oscillator in which the frequency of oscillation is changed by the variation in permeability of the magnetic core of one of the tuning ele-.

ments.

It is also an object of this invention to con-' 9 Claims. (01. 250-36) struct an oscillator which requires a consider- I able time to build up its oscillations to their-final value, but which will restart its oscillations at approximately the initial low level if the oscillations are momentarily stopped.

' Other objects and a better understanding of my invention may be obtained by referring to the following specification and claims in connection with the accompanying drawings.

Figure 1 shows an embodiment of my invention for obtaining a time delay and a gradually increasing output signal.

Figure 2 is an embodiment of my invention in which the control tube is used to gradually change the oscillator frequency.

Figure 3 shows the application of an interrupter to the circuit of Figure 1, for obtaining a time delay and gradually increasing the amplitude of the output signal at spaced time intervals.

Referring now more particularly to Figure 1, there is shown schematically a vacuum tube oscillator circuit according to my invention in which triode I3 is connected as an oscillator by coupling plate winding I9 and grid winding I6 with each other. Triode l2 and resistor II are connected in the cathode circuit of tube I3, and resistor I4 and capacitor I5 cooperate to apply a changing grid potential to triode I! which, in

turn, controls the rate of building up the amplitude of the oscillations in the circuit.

t. is to be understood that although the control elements may be'specifically referred to as I vacuum tube triodes, the scope of my invention In Figure 1, tube I3, together with capacitor I8 and windings I6 and I9 form an oscillator circuit. Tube I2 acts as an automatically variable resistance in series with the cathode of tube I3. The rate of change of cathode-to-plate resistance of tube I2 is automatically controlled by the charging of capacitor I5 through resistor I4.

To explain in greater detail the operation of my invention as sho'wn'in Figure 1, it Will be as sumed that the capacitor I5 has no initial charge. When the switch 28 to the source of direct current II] is closed, direct current passes through winding 19, tubes l2 and I3, and resistor H. Resistor I4 preferably has a high value compared sistor I4 is small compared with the current flowing through the tubes. The plate current of tube I3 passing through resistor l l causes the cathode of tube I2 to assume a positive potential with respect to its grid. The initial impedance of tube I2 is therefore large. The potential between the cathode and grid of tube I3 is equal to thesum of the potentials across tube l2 and resistor H plus the voltage induced in winding I6 by variations in the current through winding I9.

Winding I6 is connected regeneratively, that is, an increase in the current flowing through winding I9 induces a voltage in winding l6 which makes the grid of tube I3 more positive or less' negative with respect to its cathode, so that, with sufficient regeneration to counterbalance the resistance of the circuit, oscillations can occur at the natural frequency of the circuit, determined chiefly by the inductance of winding I9 and the value of capacitor I8. With tube I3 in oscillating condition, the voltage across winding I6, in-

duced from winding I9, is approximately out of phase with the A. (2'. component of the voltage across tube I2. The effect of the resistance With some circuit values, I am able to obtain satisfactory operation without the use of capacitor 32. As the capacitor I gradually becomes charged, the grid of tube l2 becomes less negative and the resistance of the tube decreases sumciently to' permit oscillations to start. The initial oscillations are of a low amplitude but gradually increase in amplitude until capacitor l5 reaches its final condition of charge.

By arranging windings I6, I! and I9 on a saturable magnetic core, I am able to cause a change in frequency to accompany the increase of amplitude of the oscillations. This change in frequency is a result of a change in the permeability of the magnetic core material resulting from the change in magnetization. When the oscillator is to be used as an audio frequency signalling generator, this simultaneous change in amplitude and frequency imparts a distinctive character to the signal and in many instances is a highly desirable feature. If a constant frequency is required, windings I6, I1 and I9 may be placed on a core whose permeability is not appreciably varied by the change in magnetization, or for higher frequencies, air core inductors may be used.

The output signal is supplied from winding ll, which may be connected directly to a load or to an amplifier which will supply the load.

The circuit of Figure 1 does not include the usual grid leak and condenser to bias the grid of tube [3. No such biasing arrangement is necessary for protecting the tube because the grid is self-biased by the plate current to a sufficiently high value to protect the tube, and the additional resistance of tube 92 and resistor H also limits the current.

Resistor il performs two functions. First, it controls the time interval between the closing of switch 28 and the beginning of oscillations generated by tube 93. Second, it provides an adjustment for the bias of tube l3-through the adjustment of tap 31. In some cases the desired circuit operation may be obtained when resistor H is omitted.

The time delay between the closing of switch 28 and the beginning of oscillations is controlled by the charging of capacitor 55 through resistor M. The adjustment of tap 35 on resistor ll adjusts the time delay obtained before oscillations begin, without appreciably affecting the initial rate of increase of amplitude of the oscillations or the final amplitude of the oscillations. In general, I have found it desirable to employ a relatively high value for resistor M and thus use a small and inexpensive capacitor i5. By making capacitor !5 small, I also obtain an advantage in circuit operation. When switch 28 is opened, the current through resistor I! de creases sharply, the charge on capacitor iS-makes the grid of tube l2 positive with respect to its cathode, and capacitor l5 discharges through tube l2. Capacitor i5 discharges rapidly to re-establish the initial circuit conditions, so that if switch 28 is reclosed soon after being opened, the circuit operation is similar to its operation under the initial conditions. If capacitor !5 is made too large it may retain a high enough voltage when switch 28 is reclosed to permit the immediate starting of oscillations at a relatively large amplitude.

The regenerative winding !6 is proportioned to.

give the desired rate of increase of the oscillations; it alsoinfiuences the time delay between the closing of switch 28 and the beginning of the oscillations. This time delay is furthered 4 justed by the adjustment of tap 3'! on resistor i In Figure 2, tube i3 oscillates continuously and control tube 92 is connected to vary the l2lnetization of the saturable inductive tuning element and thus to change the oscillator frequency without appreciably affecting its amplitude.

Theosciilator connections of Figure 2 are somewhatdifferent than in Figure 1. The windings iii and are connected in series and capacitor i8 is connected across both of them. Capacitor 2! couples the grid of tube :3 to winding l6, and grid leak 29 provides grid-current bias for the oscillator. The natural frequency of the oscillator is determined by the value of capacitor l 8 and the inductance of the combined windings i6 and iii. The oscillator connections shown in the various drawings can for the most part be used interchangeably or replaced by other standard oscillator connections to produce the desired results.

As in Figure l, the; output is supplied from winding i'i either directly or through an ampliiier.

The transformer in Figure 2 has windings 33 and 39 in addition to the windings shown in Figure l. The direct current passing. through Winding and tube l2 applies a controlled magnetizing force to the saturable core, varying its permeability and consequently changing the output frequency Impedancetil is used tolimit the passage of alternating current through winding (it because such current would constitute a load on. oscillator I3. Insome cases, the.- resistance of the tube i2 is sufiicient to limit the alternating current and impedance 38 can be omitted.

The operation of control tube I 2 in conjunction with resistors l i and i4- and capacitor !5 is simihowever, is of a different nature;

lar to the operation described. in connection with Figure 1. A modificationis introduced in Figure.

2 by the'provision of resistor 35 Whichcauses a f xed biasing current to flow through resistor H in order toprovide an increased stabilized bias. The effect of the control. tube on. the oscillator, V V Inv Figure I it wasused chiefly to control the amplitude of the oscillations and bysodoing; it simultaneously controlled the frequency. In Figure 2, it is connected in such a manner that its chief efiect is on the frequency of the oscillations.

The additional biasing. winding. 33 supplied from source it throughv resistor 34. may be used to premagnetize the saturable core to modify the effect of the control current through wind ing 39. To obtain a large frequency increase, the biasing winding 33'may be polarized and pro- 'portioned to substantially cancel thenet magnetizingv forces of windings l9 and. 39 under the initial conditions.

When switch 28 is closed, tube 83 begins to oscillate. At first, the current through winding 39 is relatively small because. of the high initial impedance of control'tube 12. As capacitor [5 gradually becomes charged: and the resistance of control. tube [2 diminishes, the direct current through winding 39 increases; The effect produced by this gradual change in current through winding 39 depends. to a great extent on the proportioning ofthe circuit elements. For example, it is. possible tohave the initial impedance of winding is. at its maximum value, in; which case the gradually increasing. current through winding 39 produces an increase in frequency. By increasing the current. through winding 33 to premagnetize thecore to asuitable degree, it.

is possible to decrease the frequency with increasing currentthrough winding 39. Tothose skilled in the art it will be evident that various other effects can be. obtained by suitable choice of the degree of premagnetization. In some cases the required variation may be obtained merely by the proper proportioning and polarizing of wind ings IS and 39 so that winding 33 may be omitted.

The circuit of Figure 2 can be used to supply an output voltage varying in amplitude as well as frequency, if desired. To obtain this effect, it is merely necessary to supply the load from winding I! through a frequency selective network.

of the operation of the circuit shown in Figure 1..

Theinterrupter can be applied in the same manner to the circuit of Figure 2.

Interrupter tube 22 in Figure 3 is an oscillator in itself; when it starts oscillating it tends to shut down the oscillations of tube I3. When tube 22 stops oscillating, the main oscillating circuit repeats its cycle of building uposcillations.

Winding 3| in Figure 3 is added to supply an additional output signal, provided by oscillator. 22. Capacitor 3!] and winding 26 set the frequency of the oscillations in this part of the circuit.

As has been. previously mentioned, Figure 1 does not show any provision .for grid current biasing. In Figure 3, as in Figure 2, grid leak 23 and condenser 2| have been added for this pur- -pose. The grid current biasing of oscillator tube I3 in Figure 3 helps to produce circuit characteristics which may be highly desirable. The additional negative bias on the grid of tube I3 tends to reduce the D. C. component of plate current below the value of current which flows during the starting condition, thereby reducing the potential drop across resistor Il andconsequently reducing the charge on capacitor I5. Therefore, if the oscillation in the circuit of tube I3 is stopped by an external cause, the charge on capacitor l may be small enough to approximate the initial condition. Thelarger current flowing through resistor II willthen cause the cathode of tube I2 to assume a positive potential with respect to its grid and the resistance of tube I2 will be suificiently high to prevent the starting of oscillations by tube I3 until sufiicient time has elapsed for capacitor I5 to charge up to the propervalue Under the proper circuit conditions the oscillations of tube I3 can be stoppedby lowering the grid potential of tube I2 by means of an impulse transmitted through capacitor 23. Then, as eapacitor I5 is slowly recharged by current through resistor I4 and by the gradual return of the charge from capacitor 23, the oscillations again gradually build up to-their maximum amplitude. To explain the operation of the interrupter cirw cuit, this circuit will be considered as a unit, ignoring the effect of the coupling capacitor 23. By ignoring the effect of capacitor 23, the tube 22 can be considered as an entirely independent oscillator unaffectedby the condition of the main oscillator circuit.

wind n s 5 em .2 ar

regeneration; The mutual inductance between these windings is considerably in excess of the minimum required to produce oscillations in the circuit. Resistor and capacitor 24 provide the grid bias for the oscillator and are proportioned so that the reactance of capacitor 23 is very low at the frequency of the oscillations, and the time constant of resistor 25 and capacitor 24 is comparable with the desired period of interruptions. When switch 28 is closed, supplying power to this circuit, oscillations begin. These oscillations are violent because the amount of regeneration is large and the grid bias does not appear immediately, until the grid current has charged the relatively large capacitor 23.

Apparently as capacitor 24 is charged by the grid current passing through it, it is charged to a voltage greater than the grid bias voltage at which oscillationscan be sustained. Once this excess voltage has been established, it is maintained for an appreciable period of time because charged through resistor 25 sufficiently to perweremega of the long time constant of capacitor 24 and resistor .25. vUnder this condition, no plate current flows through tube 22 and the oscillations stop entirely. After the capacitor 24 has dismit plate current to flow, the oscillations begin again and the cycle is repeated.

During the periods of zero plate current in tube 22 the oscillations in the circuit of tube I3 build up to their. full amplitude, and when the oscillations begin. in the circuit of tube 22, the grid side of capacitor 24 drops in potential as previously explained. This drop in potential causes part of the charge of capacitor ISto pass through capacitor 23to the grid of tube 22, with the result that the grid of tube I2 may become sufficiently negative to stop the oscillations in the circuit of tube I3. Then the operation of that part of the circuit is as has already been explained.

The output signal supplied from Winding 3| is of a .chopped nature, starting rapidly, remaining at an almost constant amplitude and then stopping suddenly. The relative lengths of the on and ofi period-s ofthese oscillations can be controlled by the selection of suitable values forresistor 29. If the amount of regeneration is large andresistor 29 has a relatively low value, the oscillations stop very quickly after starting, and do not restart until capacitor 23 discharges sufficiently to allow the plate current of tube 22 to flow again. When the chopped output signal is not used as a separate output, the rela-' tive lengths of the on and off periods may be unimportant and resistor 29 may be omitted entirely. Furthermore, in this case the frequency of these oscillations need not be accurately tuned and capacitor 33 may be omitted, so that the natural frequency of the winding 25 will determine theirequency of oscillation. V

The rapid charging of capacitor 26 transmits a sharp impulse through capacitor 23 to suddenly stop the oscillations of tube i3. If resistor 23 is made larger so that capacitor 24 charges slowly, a gradual change in bias is applied to tube I2 and the oscillations of tube I3 may be stopped ,srnall'lin comparison with capacitor I5, the. im-

applied to the circuit of Figure l, the interrupter may be applied in like manner to the circuit of Figure 2. When the interrupter circuit is used' to produce a periodic repetition of the operation of the circuit of Figure 2, the action of the interrupter is substantially the same as when applied to the circuit of Figure l. The impedance of control tube i2 is periodically varied by the action of the interrupter 22 and the output signal is correspondingly varied.

It will be apparent to those skilled in the art that other methods of coupling the circuit of tube 22 with the circuit of tubes l2 and I3 might be used with similar results. For example, resistor i4 and capacitors i 5 and 23 may be omitted and the grid of tube l2 connected directly to the grid side of capacitor 24 or to an intermediate position on resistor 25. Furthermore, various modifications shown in any one of the drawings may be applied to the other figures to adapt my invention to meet specific operating requiremerits.

It is to be understood that the present disclosure has been made only by way of example and that numerous changes in the details of con struction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

I claim as my invention:

1. An oscillator circuit comprising, in combination, an oscillator tube having at least an anode, a cathode and a control element, a control tube having at least an anode, a cathode and a control element, an output circuit having a regenerative winding, circuit means for connecting the anode of the control tube to the cathode of the oscillator tube, means for connecting the output circuit between the anode of the oscillator tube and the cathode of the control tube, means for connecting the control element of the oscillator tube to the cathode of the control tube through said regenerative winding, a timing circuit, and means for exciting theicontrol element of the control tube from the timing circuit.

2. An oscillator circuit comprising, in com bination, an oscillator tube having at least an anode, a cathode and a control element, a control tube having at least an anode, a cathode and a control element, an output circuit having a regenerative winding, circuit means for connecting the anode of the control tube to the cathode of the oscillator tube, a cathode biasing means for connecting the cathode of the control :tube to a point of reference potential, means for connecting the output circuit between the anode of the oscillator tube and the cathode of the control tube, means for connecting the control element of the oscillator tube to the cathode of the com trol tube through said regenerative winding, a timing circuit, and means for exciting the control element of the control tube from the timing circuit, said timing circuit extending from the anode of the control tube to the cathode biasing trol tube having at least an anode, a cathode and a control element, an output circuit having a re-' generative winding, circuit means for connecting the anode of the control tube to the cathode of the oscillator tube, means for connecting the output circuit between the anode of the oscillator tubeand the cathode of the control tube, means for connecting the control elementv of the oscillator tube to the cathode of the control tube through said regenerative winding, a timing circuit extending from the anode to the cathode of the control tube and including a resistor and a capacitor connected in series with each other, the control element of the control tube being connected to a point intermediate said capacitor and resistor, and interrupter-circuit means connected across said capacitor to modify the voltage im- Dressed upon the control element of the control tube.

4. An oscillator circuit comprising, in combination, an oscillator tube having at least an anode, a cathode and a control element, a control tube having at least an anode, a cathode and a control element, an output circuit having a regenerative winding, circuit means for connecting the anode of the control tube to the cathode of the oscillator tube, means for connecting the output circuit between the anode of the oscillator tube and the cathodeof the control tube, means for connecting the con-trol element of the oscillator tube to the cathode of the control tube through said regenerative winding a timing circuit extending from the anode to the cathode of the control tube and including a resistorand a capacitor connected in series with each other, the control element of the control tube being connected to a point intermediate said capacitor and resistor, and interrupter circuit means connected across said capacitor to modify the voltage impressed upon the control element of the control tube, said interrupter circuit means comprising an interrupter tube having at least an anode, a cathode and a control element, a resonant circuit having regenerative winding means, said resonant circuit being connected to the anode of the interrupter tube, said regenerative winding means being connected between the cathode and the control element of the interrupter tube, self-biasing means, circuit means for connecting the regenerative winding means and the self -biasing means between the cathode and the control element of the interrupter tube, and coupling means for connecting the self-biasing means to the control element of the control tube.

5. An oscillator circuit adapted to be energized from a source of direct current, comprising in combination, first and second valves each having an anode, a cathode and a control element, a nonlinear inductive element having first and second winding means, first circuit means for connecting the anode of the second valve to the cathode of the first'valvc, second circuit means extending from the anode of the first valve and to the cathode of the second valve for connecting said i'irst winding means and said'first and second valves in series with each other and with the source of direct current, third circuit means for connect- '9 ing the control element of. the first valve to the cathode of the second valve through said second winding means, a circuitextending from the anode to the cathode of the second valve and including a resistor and a capacitor connected in series with each other with their junction connected to the control element of the second valve, said second valve comprising a degenerative impedance in the circuit of the first valve and coopcrating with the said non-linear inductive element to vary both the amplitude and frequency of oscillations produced by the first valve.

6. An oscillator circuit comprising, in combination, an oscillator tube having an anode, a cathode and a control grid, a control tube having an anode, a cathode and a control grid, a resonant circuit having a regenerative winding, first circuit means connecting the resonant circuit in series with the anode-cathode circuits of the oscillator tube and the control tube, second circuit means extending from the cathode of the oscillator tube to its control grid and including said anode-cathode circuit of said control tube and said regenerative winding, the alternating voltage across the control tube opposing that across the regenerative winding to control the oscillations in the resonant circuit.

7. An oscillator circuit comprising, in combination, an oscillator tube having an anode, a cathode and a control grid, a control tube having an anode, a cathode and a control grid, a resonant circuit having a non-linear inductive element and having a regenerative winding, first circuit means connecting the resonant circuit in series with the anode-cathode circuits of the oscillator tube and the control'tube, second circuit means extending from the cathode of the oscillator tube to its control grid and including said control tube and said regenerative winding, the alternating voltage across the control tube opposing that across the regenerative winding to control the amplitude and frequency of the oscillations in the resonant circuit.

8. An oscillator circuit'comprising, in combination, first, second, and third valves, each having an anode, a cathode, and a grid, first resonant circuit means having first regenerative.

winding means connected between the grid of the first valve and the cathode of the second valve for exciting oscillations in the first valve, the anode of the second valve being connected to the cathode of the first valve in a series circuit including the first resonant circuit means and the anode-cathode circuits of the firstand second valves, a circuit extending from the anode to the cathodeof the second valve and including a resistor and a capacitor connected in series with each other, means for connecting a point intermediate the resistor and capacitor to the grid of the second valve, second resonant circuit means connected in the anode-cathode circuit of the third valve and having second regenerative winding means connected between the grid and the cathode of the third valve, grid-current biasing means connected in series with the second regenerative winding means whereby the third valve produces interrupted oscillations, coupling 10 means for coupling the grid-current biasin means to the grid of the second valve, said second valve comprising an impedance in the'circuit of the first valve to control the oscillations thereof in response to changes in the voltage across the grid-current biasing means.

9. An oscillator circuit comprising, in combination, first, second, and third valves, each having an anode, a cathode, and a grid, first resonant circuit means having a non-linear inductive element and having first regenerative winding means connected between the grid of the first valve and the cathode of the second valve for exciting oscillations in the first valve, the anode of the second valve being connected to the cathode of the first valve in a series circuit including the first resonant circuit means and the anode-cathode circuits of the first and second valves, a circuit extending from the anode to the cathode of the second valve and including a resistor and a capacitor connected in series with each other, means for connecting a point intermediate the resistor and capacitor to the grid of the second valve, second resonant circuit means connected in the anode-cathode circuit of the third valve and having second regenerative winding means connected between the grid'and the cathode of the third valve, grid-current biasing means connected in series with the second regenerative winding means whereby the third valve produces interrupted oscillations, coupling means for couplin the grid-current biasing means to the grid of the second valve, said second valve comprising an impedance in the circuit of the first valve to control the amplitude and frequency of the oscillations in the first valve in response to changes in the voltage across the grid-current biasing means.

HENRY M. HUGE.

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